BANGUI (Reuters) - A Rwandan soldier serving with the U.N. peacekeeping mission in Central African Republic shot dead four Rwandan troops and wounded eight others on Saturday before committing suicide, according to the Rwandan Defense Ministry.

The incident occurred at around 5:45 a.m. (0445 GMT) at the Rwandan battalion's headquarters in the capital Bangui.

"Investigations have immediately commenced to establish the motive behind this deplorable shooting," spokesman Brigadier General Joseph Nzabamwita said. "We suspect terrorism, without ruling out mental illness as the cause."

The statement said the injured soldiers had immediately been transported to a hospital in Bangui for treatment.

Central African Republic descended into chaos in March 2013 when predominantly Muslim Seleka rebels seized power, triggering reprisals by "anti-balaka" Christian militias who drove tens of thousands of Muslims from the south in a de facto partition.

The U.N. mission in Central African Republic, known as MINUSCA, was deployed to shore up the precarious stability established under a transitional government.

Rwanda has roughly 850 peacekeepers deployed in the country.

MINUSCA said it had opened an investigation into the incident.

(Reporting by Crispin Dembassa-Kette in Bangui; additional reporting by Clement Uwiringiyimana in Kigali; writing by Joe Bavier; Editing by Edith Honan and Kevin Liffey)